adding blinker04, this uses the ARM timer

blinker04/Makefile

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+
+ARMGNU ?= arm-none-eabi
+
+COPS = -Wall -O2 -nostdlib -nostartfiles -ffreestanding 
+
+all : blinker04.hex blinker04.bin
+
+clean :
+	rm -f *.o
+	rm -f *.bin
+	rm -f *.hex
+	rm -f *.elf
+	rm -f *.list
+	rm -f *.img
+
+novectors.o : novectors.s
+	$(ARMGNU)-as novectors.s -o novectors.o
+
+blinker04.o : blinker04.c
+	$(ARMGNU)-gcc $(COPS) -c blinker04.c -o blinker04.o
+
+blinker04.elf : memmap novectors.o blinker04.o 
+	$(ARMGNU)-ld novectors.o blinker04.o -T memmap -o blinker04.elf
+	$(ARMGNU)-objdump -D blinker04.elf > blinker04.list
+
+blinker04.bin : blinker04.elf
+	$(ARMGNU)-objcopy blinker04.elf -O binary blinker04.bin
+
+blinker04.hex : blinker04.elf
+	$(ARMGNU)-objcopy blinker04.elf -O ihex blinker04.hex
+

blinker04/README

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+
+See the top level README for information on where to find the
+schematic and programmers reference manual for the ARM processor
+on the raspberry pi.  Also find information on how to load and run
+these programs.
+
+This example uses the ARM timer, not the free running ARM timer which
+counts up (see blinker03) but the other timer that counts down.
+
+A few more typos in the datasheet.  It is an SP804 not AP804 (page 196).
+Page 197, bit 1 32 bit counter not 23 bit counter.  Page 198 neither
+the raw nor masked IRQ registers are at address 0x40C.
+
+So if you want to poll an arbitrary time with a free running timer you
+take a reference count, and then take a sample, wait for the difference
+between the sample and reference count.  You have to know if it is an
+up or down counter.  You can turn this timer into a free running timer
+by setting the load registers to all ones.  What you can also do with
+this kind of timer that you cannot with a free runing timer is set the
+load registers to some number of ticks (minus 1) and it will roll over
+the counter at that rate.  Often these kinds of timers have an interrupt
+as does this one.  And you can poll the interrupt bit without havingt to
+actually configure an interrupt.  This example sets the prescaler to
+divide by 250.  The clock as running here is 250Mhz, so this takes it
+down to 1Mhz, 1000000 clocks per second.  Now if we set the load registers
+to 4 million counts (minus 1) then every 4 million counts at 1 million
+per second is 4 seconds.  Every 4 seconds the timer interrupt will fire.
+Which you can read in the raw irq (not masked) register.  Once it is
+set you have to write anything to the clear interrupt register.  If you
+were to set up an interrupt service routine, you would clear that
+interrupt in the interrupt handler.
+

blinker04/blinker04.c

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+
+//-------------------------------------------------------------------------
+//-------------------------------------------------------------------------
+
+extern void PUT32 ( unsigned int, unsigned int );
+extern unsigned int GET32 ( unsigned int );
+extern void dummy ( unsigned int );
+
+#define ARM_TIMER_LOD 0x2000B400
+#define ARM_TIMER_VAL 0x2000B404
+#define ARM_TIMER_CTL 0x2000B408
+#define ARM_TIMER_CLI 0x2000B40C
+#define ARM_TIMER_RIS 0x2000B410
+#define ARM_TIMER_MIS 0x2000B414
+#define ARM_TIMER_RLD 0x2000B418
+#define ARM_TIMER_DIV 0x2000B41C
+#define ARM_TIMER_CNT 0x2000B420
+
+#define SYSTIMERCLO 0x20003004
+#define GPFSEL1 0x20200004
+#define GPSET0  0x2020001C
+#define GPCLR0  0x20200028
+
+#define TIMEOUT 4000000
+
+//-------------------------------------------------------------------------
+int notmain ( void )
+{
+    unsigned int ra;
+
+    ra=GET32(GPFSEL1);
+    ra&=~(7<<18);
+    ra|=1<<18;
+    PUT32(GPFSEL1,ra);
+
+    PUT32(ARM_TIMER_CTL,0x003E0000);
+    PUT32(ARM_TIMER_LOD,4000000-1);
+    PUT32(ARM_TIMER_RLD,4000000-1);
+    PUT32(ARM_TIMER_DIV,0x000000F9);
+    PUT32(ARM_TIMER_CLI,0);
+    PUT32(ARM_TIMER_CTL,0x003E0082);
+
+    while(1)
+    {
+        PUT32(GPSET0,1<<16);
+        while(1) if(GET32(ARM_TIMER_RIS)) break;
+        PUT32(ARM_TIMER_CLI,0);
+        PUT32(GPCLR0,1<<16);
+        while(1) if(GET32(ARM_TIMER_RIS)) break;
+        PUT32(ARM_TIMER_CLI,0);
+    }
+    return(0);
+}
+//-------------------------------------------------------------------------
+//-------------------------------------------------------------------------

blinker04/memmap

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+
+MEMORY
+{
+    ram : ORIGIN = 0x00000000, LENGTH = 0x1000
+}
+
+SECTIONS
+{
+    .text : { *(.text*) } > ram
+    .bss : { *(.bss*) } > ram
+}
+

blinker04/novectors.s

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+
+.globl _start
+_start:
+    b reset
+
+reset:
+    mov sp,#0x1000
+    bl notmain
+hang: b hang
+
+.globl PUT32
+PUT32:
+    str r1,[r0]
+    bx lr
+
+.globl GET32
+GET32:
+    ldr r0,[r0]
+    bx lr
+
+.globl dummy
+dummy:
+    bx lr